Confinement and shape effects on the optical spectra of small CdSe nanocrystals

Albe, V.; Jouanin, C.; Bertho, D.

doi:10.1103/physrevb.58.4713

Cited by 66 publications

(47 citation statements)

References 32 publications

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“…Later development of the QC theory shows that the relation of [491], and 1.37 [485]) fits better the size-dependent PL blueshift and the n values vary from source to source. Nevertheless, it is important to recognize that the QC premise is indeed a very helpful first-order approximation, and can be used to estimate changes in energy levels, exciton and related energies, as a function of dot size.…”

Section: Outstanding Models 721 Quantum Confinementmentioning

confidence: 99%

“…(i) The band gap expands with reducing particle size, which gives rise to the blueshift in the PL and photo-absorbance (PA) spectra of nanometric semiconductors such as Si oxides [73,478,479,480], IIIeV [481] (GaN [482,483], InAs [484], GaP, and InP [485,486]) and IIeVI (CdS [487e489], ZnS [490], CdSe [491,492], ZnTe [493], CdTe/CdZnTe [494]) compounds. (ii) The energies of PL and PA involve the contribution from electronephonon coupling that shifts the optical band gap E G from the true E G by the well-known value of Stokes shift arising from electronephonon interaction that also changes with solid size [47].…”

Section: Introductionmentioning

confidence: 99%

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Size dependence of nanostructures: Impact of bond order deficiency

Sun

2007

Progress in Solid State Chemistry

817

717

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Section: Outstanding Models 721 Quantum Confinementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Size dependence of nanostructures: Impact of bond order deficiency

Sun

2007

Progress in Solid State Chemistry

817

717

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“…12 The shape of the nanocrsytals has even sometimes been described in terms of thin plates rather than spheres. 10 The consequences of shape uncertainty may be important because ellipticity has been predicted to affect strongly the oscillator strengths of CdSe nanocrystals 13 and has been suggested as a factor that might affect the hole level splitting in CdS samples. 4 Therefore, we carried out calculations for several nanocrystal sizes and shapes within the experimental uncertainty.…”

Section: Introductionmentioning

confidence: 99%

Tight-Binding Method and Multiband Effective Mass Theory Applied to CdS Nanocrystals: Single-Particle Effects and Optical Spectra Fine Structure

et al. 2004

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Optical spectra of CdS nanocrystals are interpreted by using both the atomistic tight-binding method and multiband effective mass theory. Both methods correctly describe the energy splitting between the two lowest optically active transitions and their relative strengths, providing the same labeling of the two main absorption peaks of the spectrum. Our calculations unambiguously show that these peaks correspond to the 1S 3/2 f 1s and 1P 3/2 f 1p transitions. Both zinc blende and wurtzite-type structures for CdS nanocrystals are considered. Similar optical spectra are predicted for the two lattice structures. We also study how the spectrum, and in particular, the 1S 3/2 -1S 1/2 splitting, is changed by modifying parameters, within the experimental uncertainties, including size and shape fluctuations, surface passivation and spin-orbit coupling. Our results are robust to small variations in all of these parameters. IntroductionProgress in experimental techniques allows both the synthesis and characterization of high quality, monodisperse nanocrystals with a well-established shape, crystal structure, and a consistent surface derivatization. 1-3 Transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) are used in combination with computer simulations to characterize nanocrystallite structural features. TEM allows imaging of individual nanocrystals and the development of a statistical description of the size and shape of the particles in a sample, whereas XRD determines the crystal structure. Different spectroscopies, such as fluorescence line narrowing and hole burning, are able to eliminate the effects of inhomogeneous broadening due to their size-selectivity so that the near-band-edge electronic fine structure can be observed. 2 Recently, attenuated low-energy photoelectron spectroscopy, A-LEP, has been proposed as a new technique for studying the hole states of the quantum particles (QPs), including the splitting between the light/heavy hole and split-off bands. 4 Both the effective mass method (EMM) and tight-binding (TB) theory have been successfully applied to model the optical properties of quantum dots and nanocrystals. The multiband effective mass theory has correctly predicted a large resonant Stokes shift in small CdS nanocrystals 5 consistent with recent photoluminescence excitation measurements, 6 whereas the atomistic tight-binding theory has provided a detailed description of the excitonic fine structure for multilayer nanocrystals with changes in composition on the monolayer scale. 7-9 In the abovementioned studies, the optical properties and the various observed phenomena are described well in terms of a single isolated dot.In this paper, we present both tight-binding and multiband effective-mass theory to describe the electronic states and optical response of CdS nanocrystals. We determine the effects of

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“…Bandgap E G expansion gives rise to the blueshift in the PL and photoabsorbance (PA) energy of nanometric semiconductors such as Si [2], Si oxides [3][4][5][6], III-V [7] (GaN [8,9], InAs [10], GaP and InP [11,12]), and II-VI (CdS [13][14][15], ZnS [16], CdSe [17,18], ZnTe [19], CdTe/CdZnTe [20]) compounds. The energy shifts are controllable by changing the particle size or by pore formation.…”

Section: Observationsmentioning

confidence: 99%

Bandgap Expansion: Photon Emission and Absorption

Sun

2014

Springer Series in Chemical Physics

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• The E G of a semiconductor is proportional to the first Fourier series coefficient of the interatomic potential.• Skin-resolved bond contraction and entrapment perturb that the Hamiltonian originates and the increased fraction of undercoordinated atoms expands the E G .• Energies of photon emission and photon absorption are superposition of the interatomic binding energy and the electron-phonon coupling i.e., Stokes shift.• Polarization of the dangling bond electrons creates the mid-gap states and band tails, which lowers the quantum efficiency of photon emission; hydrogenation could annihilate such defect states.• Graphenes with arm-chaired or reconstructed zigzag edges are semiconductor like because of the annihilation of the edge polarization by quasi-p bond formation between the nearest carbon atoms along the edges; graphenes with zigzag edges behave like metal because of the edge localized and polarized states in the mid-gap region.

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Confinement and shape effects on the optical spectra of small CdSe nanocrystals

Cited by 66 publications

References 32 publications

Size dependence of nanostructures: Impact of bond order deficiency

Size dependence of nanostructures: Impact of bond order deficiency

Tight-Binding Method and Multiband Effective Mass Theory Applied to CdS Nanocrystals: Single-Particle Effects and Optical Spectra Fine Structure

Bandgap Expansion: Photon Emission and Absorption

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